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F. HOLMSTROM,1n. TELEPHONE REFRODUCEIl APPLICATION mtu noma. wir. szuzwzu sinn. 192|.

1,430,082, PatentedSept 26, 1922.

- o' P'g E' i@ Inventar P-ankHmms'z-ajf i 25 means.

c |50 6, clamping between 515 strument may be Patented Sept. 26, 1922.

lUNITED STATES :PATENT oFFlcs.

FRANK HoLNisTnoM, JR., or cHIcAGo, ILLINOIS, AsSIGNoR, BY MEsNE ASSIGNMENTS,

To CHARLES a. BENNETT, or K aNsAsfo1Tv, MIssoUaI.

` TnLErHoNE BErRonUcE'n..

` Application filed November 3, 1917, ,Serial No. 200,218. Renewed September 22,1521. Serial No. 502,511.

T 0 all whom it may concern:

Beit known that I, FRANK HoLMsTRoM,

Jr., a citizen of the United States of America, andlresident of Chicago, Cook County,

" 5 Illinois, have invented certain new and useful Improvements in Telephone Reproducers, of which the following is a specification.

My invention relates to improvements in telephone reproducers.

" l'Among the objectsof my invention-are the following:

character that will 4.permit the use of a uni- 'tary'mcrophone element removable andfrc- 15 plaoeable as a whole from and in relation'to the receiving part of the device` To'produce means for properly 'securing themicrophone element in juxtaposition to the receiving part. f-

' To produce means in such a, device, wherebyfall tension may be relieved'from the dia phragm proper and such that after the element is secured in position tension 'may vbe applied to the diaphragm by adjusting To provide other details of improvement tending to increase the eiciency and serviceability of a reproducer of the above character.

The means for accomplishing the foregoing'and other useful ends are hereinafter set forth and claimed. Referring to ltheI accompanying drawing Fig. l'shows a side elevation of the instru 315 ment with a portion of the casing cut away vand the micr'ophonevandlts associated parts in cross section in a plane with the limbs of a-m'agnet. e t y f Figure 2 is a` sectional view of the instru- 40 nient'looking in the direction indicated-by the' arrows along line A-B in Fig. l'show- Zing the method used in mount-ing the microphone cell. e js As shown in the drawings thisl invention 6 comprises a magnet which responds tocurrent changes to vibrate the diaphragm of ya 'microphone cell. In Fig. 1. is shown a magnet having two steel limbs 3 and 4, which are clamped together at the lower end by'abolt iron 6 of suitable vthickness Ito keep them apart`the proper distance. This piece of iron is extended through the lower end of the casing to form a'lug by which said inmounted' and is also held the limbs a piece of soft .'to the casing dloylmeans of screws 7 to keep the 'magnet 1n "a firm position in the casing. N ear the upper end the two limbs are clamped togetherbyral brass bolt 8 clamping a brass piece9 and a soft iron .pole piece 10 between said limbs. 'A This bolt, furthermore,

- To provide means 1n a Idevice of the -above 'f'lhi'sarmaturihasone end resting up against --link 16 is"V connected. yThrough the upper Aendof the link 16 is a'lever 17 which is sup yportedaone end by a fulcrum onV the end of 1the screw"318,' which screw Vis in turn Amounted-in a'pivoted or tiltinga'rm 19 which isadaptedto be tilted about an axis 20 when `the screw -21is adjusted one way or another and which risheldagainst the ead of said "screw 214 bymeans ofa spiralspring 22. The other'end'of the lever '17 is supported by a-1ink23 whichi is connected at the other end to thet nlovable' electrode: and front diaphra'gm `of"amicrophone cell. When the screw,i`sjoperated it raises or lowers the ivfulcrum andthereby 4regulates the air Vgap between' the 'armature 14 and the magnet 13,

`and when the screw 18 is operated it forces the lever 11 nearerto'or further away frorn thelink4 16 therbyvarying the 'leverage of` said 'lever-iso as to secure the desired leverage between the' armature and the diaphragm 1n 'order'to amplify :the vibration of said armature --when transmitted to the microphone.

#Mounted fpqn the "end of the supportslly "and112 is'a plate 24:,hav1ng a circular opening? inthe "center thereof, and a bridge which is insulated from the supports 11 and 12 by fibrewasher's and secured to the ends of 'supported-1' and 12 bymeans of suitable studs 'andfnits Sl'dably mounted in the lbridge 25 is 'a microphone of well known type which forms a complete unit and comprises" "a cup 26 having a. plug extension which isfcIampedinto an opening inthe bridge 25, said cup having a back electrode mounted therein and having a cap 27 which clamps a mica diaphragm 28 between itself and said 'ca-p. The mica diaphragm carries a front o'r movable electrode and a stud to which the link Q3 is secured, the opening bet\\'ee1rsaidf1fiont and back :electrodes being nearly filled with granular carbon 'in the usual manner. Securely fastened to the stud .5 ofthemica'diaphragin is a spring29 which bridges across-the open-ing in the plate 24 and the ends of which rest on a counterbored surface on the upper side of said plate, this Vspring Atends,normally to hold themicrophone cell up toward the bridge .25, and is used tomaintain, a certain-.tension toward the, mica. diaphragmV when the .cell is pressed towarld 'the plateQA and clamped. by means of.the=set YscrenO (Fig ,.2). .It willfbe lrlunderstood. that: the magnetism of thepermanent. mngnetcomprising limbs S2M-andl 4 tends todrawthe armature llltoward the Ipolefpiece 10, butthe tension of-the lspring 42). exerted on -.the lever `17 holds said armature at a, slightdistance from the said pole piece. according totheadjustment of. .the screw,2l. lNow .when telephonic-or other varying currents are passed i through the magnet. 13, tbemagnetism of the .permanent magnet is increased.and .decreased Vthereby and the armature. 14- is vibrated. These vi- .brations will vvbe :transmitted to the ,-dia i phragm-nd -front electrode of the: micro- E phone cell 4` by.means of the lever and link arrangement, and thenamplitude of said vibrations .will vbe .somewhat increased by. the .actionof said lever,4 sothfat when a circuit is connected through said cell and a current assed therethrough,v said current will be ,.85 uctuated bythe increasingand decreasing .of theresistance of saidcell in :swell-known manner. Cl amped, one 4,on either-side 4pt rthe ,limbs 3.and lL -are .a.pair of'. .terminal blocks of insulating .material onlyone of which is shown at;l 3l. The block-,31 carriesay pair of terminals-f 32..and.33, the 4terminal 13B-being connected to one terminal. ofthe-magnet Al2 ...and [the terminal. 32 being .connected by meansot the pla-te 24with .the frontV electrode of the microphonecell. :The otherterminal block (not shown) also-has= apairiof terminals mounted thereon, lone of which is connected 'to the other terminal of themag- .net 13.and the other 01h-which is connected by. meansv of the:` bridge 25.. and cu ...Q6-with thebackelectrode ofsaidcell. ecuredto the softrironpieceby means of suitable -screwsisacap provided with a pair of hushed. openings through which-.the `-wires leadingffromthe terminals 32, 33, etc.4 may be extended. .A casingentirely encloses ,saidlinstrumentandis.fastened in the cap 34 by ,snitablescrews Itwill therefore be seen-'that I haveprof-60 .,vided a, v'eryeicientform oftele hone re- Apeaten.onamplifier and one W-hc is-very .easily repaired,.the instrument being sol de -signed ,that .iniorder to repair or change the microphone cellonly the bridge 25 need be l 65,remo1/ed, -afterwvhichthe cell',-whch is. as-

'ing an armature, a Ilresilient element` sesembled as a unit, may be very easily removed. l

What I claim as my invention is:

1. In a reproducer, a receiver element hav- 70 curedto oppose'the magnetic pull of the re- .ceivermagnet armature to hold it Way from 'the magnet polepiece, means for adjusting tthe opposing'. forces. to .regulate the distance between armature and polepiece, a microphone unit, meansA forlinking. the of-said unit tosaid element aftergtlleipill of the 4opposing:forces ,is adj usted.\and means fornancbgoring the. back of the; miclloplwne .after.,the..adjustment. 2. :In a reproducer, areceiyer element havfing. lan. armaturefia resilient. element secured magnet armature to hol hawayrnqm-.the .magnet;.po1epiece,'-lmeansi.iorhadJustingthenB opposing forces to regulate the-.distane..be

tweemarmature and polepiece, a. microphone nuit, means -for linking tlieidiaphnagmigof said unit tosaidelement afterthepull of-ythe opposing, forces;V is,.adjusted, meansiA-fonfian-n choring the backiofthe microphone abenthe adjustment, .said lastmmeams .including a' i bridge over Jthe .microphone secured ,toathe magnet structure.

.-3. Inia reproducerfa receigerielement .hav-95 ,ing an. armatnre,.a .resilient elementi secured to oppose 'the magnet :pull-,ofthe receiver magnet armature-dto. .h old Y itawa f fnompthe Y magnet fpolepiecdymeans for -adgnst-ingthe opposing forces to regulate the distancenbe-aloo Y tween 4armature amd-'..polepiece a microphone unit,1v means. vieri*1inki1;lg=.the\diaphragmnot i said unit? to said'element"after:l the -pplhof the opposing forces is adjusted, means-for V.anchoring the: ,becket the'microphoneqaternlo i the. adjustment, -sad lasti means including. .a

bridge over the microphone. securedgto the magnet structures-sa-idY bridge'. ontheqside of .,the resilientmember away from the: armauture.

,1110 4. In `a .rep-reducen, a receiver element having an armature, .a resilient i element:secured to oppose the magnet ull of thefreceiver magnet armature to ,ho d ,-it..away.: fromi the .magnet1 polepiecewmeansforiadustmgmheflw opposing for-ces' to regulate the 4istanceabe tween armature.; and .po1epiece,l a, microphone unit, means for linking the diaphragmfm 5. In .la reproducer,. al.- receiver .Ahavingifi a magnet, anaarmature, an .extensionsupportilao attached to said magnet extending beyond said armature, a spring plate over said armature sustained by said extension, a connecting link from said armature to said spring serving to hold the armature away from the magnet polepiece, said spring balancing the magnetic pull, a microphone unit having its diaphragm secured to said spring on the side away from the armature, a bridge over said microphone having its ends anchored to said extension, a pin projecting from the back of said unit through an opening in said bridge and means for securing said pin to said bridge after the spring and magnetic pull are balanced.

6. In a reproducer, a receiver element hav- 4ing an armature, a resilient element secured to oppose the magnetic pull of the receiver magnet armature to hold it away from the magnet polepiece, means for adusting the opposing forces to regulate the istance between armature and polepiece, a microphone unit, and means for anchoring the back of the microphone after the adjustment in a position free from any of the normal pull of the receiver magnet.

7. In a reproducer, a receiver element having an armature, a resilient element seycured to oppose the magnetic pull of the receiver magnet armature to hold it away from the magnet polepiece, means for adjusting the opposing forces to regulate the distance between armature and polepiece, a microphone unit, means for anchoring the back of the microphone after the adjustment, said last means including a bridge over the microphone secured to the magnet structure in a position free from any of the normal pull of the receiver magnet.

8. In a reproducer, al receiver element having an armature, a resilient element secured to oppose the magnet pull of the receiver magnet armature to hold it away from the magnet polepiece, means for adjusting the opposing forces to regulate the distance between armature and polepiece, a microphone unit, means for anchoring the back of the microphone after the adjustment, said last means including a bridge over the mcrophone secu-red to the magnet structure, said bridge on the side of the resilient member away from the armature in a position ree from any of the normal pull of the receiver magnet.

9. ln a reproducer, a receiver element having an armature, a resilient element secured to oppose the magnet pull of the receiver magnet armature to hold it away from the magnet polepiece, means for adjusting the opposing forces to regulate the distance between armature and polepiece, a microphone unit, means for anchoring the back of the microphone after the adjustment, said last means including a bridge over the microphone secured to the magnet structure, said brid e on the side of the resilient member away rom the armature, said force adjusting means located between the resilient member and the armature in a position free from any of the normal pull of the receiver magnet.

10. In a reproducer, a permanent magnet receiver, a microphone unit and a resilient clement, means for balancing the pull of the resilient element against the pull of the receiver magnet, and means for thereafter anchoring the microphone element and to render the same responsive to the receiver element while relieving the microphone element of any of the receiver magnet pull during the time that the receiver magnet is not responding to voice currents.

Signed by me at Chica o, Cook County, Illinois, this 19th day of ctober, 1917.

FRANK HOLMSTROM, J B. 

